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A call for 2nd stage cooling from the thermostat closes
the R to Y2 circuit on the control board. The blower motor
ramps up to 100% of the selected cooling air flow. When
the demand for cooling is met, the blower ramps down
to Y1 until satisfied, then ramps down to continuous fan
cfm (38% of high stage cooling) for 45 seconds before
completely shutting down the blower.
Heat Pump
For heat pump operation, clip the jumper wire located
below the O terminal on the integrated ignition/blower
control board. In heat pump mode, a call for heat will
result in the circulating air blower operating at the selected
cooling airflow after a brief ramp-up period.
Control Diagnostics
Troubleshooting
Make the following visual checks before troubleshooting:
1. Check to see that the power to the furnace and the
integrated ignition/blower control board is ON.
2.
The manual shutoff valves in the gas line to the furnace
must be open.
3.
Make sure all wiring connections are secure.
4.
Review the Sequence of Operation.
Start the system by setting thermostat above room
temperature. Observe system response. Then use the
information provided in this section to check the system
operation.
The furnace has a built-in, self-diagnostic capability. If a
system problem occurs, a fault code is shown by a red LED
on the control board. The control continuously monitors its
own operation and the operation of the system. If a failure
occurs, the LED will indicate the failure code. The flash
codes are presented in Table 12.
Fault Code History Button
The control stores the last five fault codes in memory. A
push button switch is located on the control. When the
push button switch is pressed and released, the control
flashes the stored fault codes. The most recent fault code
is flashed first; the oldest fault code is flashed last. To
clear the fault code history, press and hold the push button
switch in for more than 5 seconds before releasing.
High Heat State LED
On models, a green LED is provided on the control board
to indicate high heat state (see Table 13).
Page 40 of 53
CFM LED
On models equipped with a variable speed motor, an amber
LED is provided on the control board to display CFM. To
determine what CFM the motor is delivering at any time,
count the number of times the amber LED flashes. Each
flash signifies 100 CFM; count the flashes and multiply by
100 to determine the actual CFM delivered (for example:
10 flashes x 100 = 1000 CFM).
LED Status
LED Off
LED On
1 Flash
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes
7 Flashes
8 Flashes
9 Flashes
Table 12. Failure Codes - Red LED
LED Status
LED Off
LED On
LED Flashing
Table 13. High Heat State - Green LED
Issue 2341
Fault Description
No power to control or control
hardware fault detected
Normal operation
Flame present with gas valve off
Pressure switch closed with inducer off
Pressure switch open with inducer
energized
Primary Limit, Secondary Limit, or Roll-
Out switch open
Not used
Pressure switch cycle lockout
Lockout due to no ignition
Lockout due to too many flame
dropouts
Incorrect polarity and phasing
Description
No demand for high heat
High heat demand, operating normally
High heat demand, high pressure
switch not closed
508405-01
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